This invention relates to a thermostatic mixing valve and more particularly to a construction within a thermostatic valve that increases mixing of cold and hot water supplied to the mixing chamber.
Hot water and cold water supplied to a thermostatic mixing valve must be efficiently mixed in order for a thermostatic mixing valve to optimally perform its thermostatic function. The water must be sufficiently mixed before it comes into contact with the thermostatic element which controls the operation of the thermostatic valve. Commonly the thermostatic element includes a wax filled case and a piston which is moved by thermal expansion of the contained wax. Consequently, in many better quality thermostatic mixing valves, structures are introduced to promote early and complete mixing of the cold water and hot water supplied to the mixing device before the mixed water comes into contact with the case.
German patent number 4,423,240 discloses a disc mounted on the thermostatic element. The disc periphery is located close to the hot water intake apertures located in the perimeter wall of the mixing chamber. The cold water enters the mixing chamber via a narrow space between the periphery of the disc and the perimeter wall of the mixing chamber. In this way, the two currents of cold water and hot water meet at right angles to each other to provide a certain level of mixing. However, this known construction has some disadvantages. First of all, an additional element in the form of a disc is introduced which increases the cost of manufacture and complicates assembly of the thermostatic mixing device. In addition, the disc needs to be positioned to form a narrow annular space within the mixing chamber adjacent the perimeter wall of the mixing chamber thereby calling for the necessity of precise manufacturing tolerances, especially with regards to the centering of the disc. Furthermore, the necessity for the space to be narrow in order to be effective undesirably reduces in the maximum flow rate provided by the mixing device. Finally, the pressure drop due to the passage of the cold water through the narrow space gives rise to a force which applies a dynamic drag to the disc. The dynamic drag acts against the biasing spring in the thermostatic system and interferes with its operation which may cause instability in some particular circumstances.
What is needed is a thermostatic mixing valve construction capable of effectively promoting early mixing of the cold water and the hot water supplied to a mixing device by a particular arrangement of existing elements without the addition of an added element. What is also needed is a construction that does not require overly precise manufacturing tolerances or does not appreciably increases the cost of production of a thermostatic mixing device. Another need is to reduce the phenomenon of dynamic dragging to the point where it becomes negligible in such a thermostatic valve and where the construction does not impose restrictive limits on the maximum flow rate admitted by the mixing valve.
In accordance with one aspect of the invention, a thermostatic mixing valve includes a housing with an inlet port for intake of hot water, an inlet port for intake of cold water and a mixing chamber located in the housing and defined by a perimeter wall. A discharge outlet for discharging mixed water leads from the mixing chamber. Preferably, passages leading to the mixing chamber are operably connected to the inlet ports for hot and cold water respectively. A slide valve is operably movable in relation to the perimeter wall of the mixing chamber and placed so as to control the opening and closing of at least one of the passages or ports for intake of hot water and cold water. A partition is affixedly connected to the slide valve. The partition has a crossing passage located in proximity to the partition""s periphery. The housing contains a surface in proximity to the passage for intake of hot water that is inclined toward the interior of the mixing chamber and toward the partition and opposes the crossing passage in the partition.
A spring is located in the housing and connected to the valve to bias the slide valve in a direction corresponding to an opening of the passage for intake of hot water and to a closing of the passage for intake of cold water. A thermostatic element operating by thermal expansion is operably interposed between the partition and the housing to assist the slide valve to move in a direction corresponding to a closing of the passage for intake of hot water and to an opening of the passage for intake of cold water when the thermostatic element undergoes thermal expansion.
Preferably the slide valve is annular in shape and centered about a central axis of the valve with the passage for hot water and the passage for cold water being circumferentially arcuate about the central axis. It is also desirable that the partition has a plurality of crossing passages circumferentially spaced in proximity to the periphery of the partition. The inclined surface is also preferably annular in shape. In one embodiment, the inclined surface is substantially rectilinear in section and forming a frusto-conical surface. In another embodiment, the inclined surface is curvilinear in section and forms part of toroidal surface.
In one embodiment the housing includes a separate body member which houses the inlet ports. The mixing chamber is defined by the perimeter wall and a first insert member and second insert member. The passage for intake of cold water is located between the perimeter wall and the first insert member. The passage for intake of hot water is located between the perimeter wall and the second insert member. Alternatively, the perimeter wall can be integrally formed with the valve housing. The housing has a separate first insert member and a second insert member. The passage for intake of cold water is located at the perimeter wall in proximity to the first insert member and the passage for intake of hot water is located at the perimeter wall in proximity to the second insert member. The inclined surface is formed on the second insert member.
In another embodiment, the perimeter wall and the partition are formed in a separate member mounted in the body. The separate member and the first and second insert members are connected together to form a cartridge assembly which houses the thermostatic element and the spring.
In one embodiment, it is desirable that an inner facing peripheral surface of the second insert member is interposed between the inclined surface and the discharge outlet and is inclined in a direction away from the central axis as its distance from the partition increases.
In accordance with another aspect of the invention a thermostatic mixing valve includes a housing with an inlet for hot water, an inlet for cold water, and a mixing chamber in communication with said inlets. The thermostatically controlled slide valve is slidably mounted in the mixing chamber for controlling the extent of opening and closing of the inlets. The partition is located in the mixing chamber within the slide valve between the inlets. Crossing passages allow water from one inlet to pass the partition in the slide valve to the discharge outlet. The other inlet has a surface inclined to direct water entering therethrough toward the partition.
Because of the above described conditions, the cold water which enters the mixing valve and passes through the slidable valve is admitted to the mixing chamber via the peripheral passages of the partition, preferably in the form of several substantially parallel jets which are close to the perimeter wall of the mixing chamber. Hot water which enters the mixing valve and comes through the slide valve is admitted to the mixing chamber in contact with the inclined surface and consequently flows in a direction which is towards the interior and towards the partition. In this way the flow of hot water encounters the flow of cold water presenting an axial component of opposed velocities so that a high turbulence is generated which causes very effective mixing of the hot and cold flows before they come into contact with the thermostatic element.
This effect is obtained without introducing complexity by any additional elements or without causing any major problems in construction or assembly. Since the passages which cross the partition may be of any size, at least within certain limits, the arrangement does not cause any restriction in the maximum flow rate admitted by the thermostatic mixing valve. The cold water encounters less hindrance to its passage and does not undesirably provide any significant dynamic drag. The construction according to the invention does not entail any critical relative position of parts, and therefore does not entail the necessity of undesirably precise manufacturing tolerances.
Finally, the inner facing peripheral surface of the second insert member which may also be inclined as described, causes a cavitation which, in its turn, then increases the turbulence, which makes mixing more effective.